A non-contact power transmission device equipped with a ground-side device and a vehicle-side device. The ground-side device has a primary-side coil to which alternating-current power is input. The vehicle-side device includes a secondary-side coil, a battery, a secondary-side matching device, and a charging device. The secondary-side coil receives alternating-current power from the primary-side coil in a non-contact manner. The secondary-side matching device is provided between the secondary-side coil and the battery, and has a predetermined fixed inductance and fixed capacitance. The charging device has a switching element that performs a switching operation with a prescribed cycle. The charging device adjusts the duty ratio of the switching operation in accordance with the impedance of a load.
